System and method for venting pressure from an integrated circuit package sealed with a lid

ABSTRACT

A system and method is disclosed for venting pressure from an integrated circuit package that is sealed with a lid. During a surface mount process for mounting a ball grid array integrated circuit package to a circuit board the application of heat ( 1 ) weakens the solder that seals a soldered lid, and ( 2 ) increases vapor pressure within the integrated circuit package. This may cause the soldered lid to move out of its soldered position. The present invention solves this problem by providing an integrated circuit with a solder mask that has a plurality of solder mask vents that form a plurality of vapor pressure vents through the solder. The vapor pressure vents prevent the occurrence of any increase in vapor pressure that would shift the soldered lid out of its soldered position. An alternate embodiment vents pressure through an epoxy layer that is used to attach a lid by epoxy.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention is directed, in general, to integratedcircuits and, more specifically, to a system and method for ventingpressure from an integrated circuit package that is sealed with a lid.

BACKGROUND OF THE INVENTION

[0002] It is well known that the operation of an integrated circuitgenerates heat. In many applications an appreciable amount of heat maybe generated by the operation of an integrated circuit. In someinstances the heat from the operation of an integrated circuit may bedissipated into the surrounding ambient atmosphere through convection.In other instances the amount of heat to be removed that is generated byan integrated circuit may require the use of an external coolingmechanism. An example of an external cooling mechanism is a fan thatblows cooling air over an integrated circuit to carry away heat.

[0003] In some instances the amount of heat that is generated by anintegrated circuit may require a relatively large amount of cooling inorder to dissipate the generated heat. For example, a sustainedoperation of an integrated circuit in a high power application mayrequire an increased level of cooling in order for the integratedcircuit to function properly. There is therefore a need for an efficientheat removal process to cool an integrated circuit while the integratedcircuit is operating.

[0004] Integrated circuit packages exist that remove heat from anintegrated circuit die by conducting heat from the integrated circuitdie into a thermally conductive slug. The heat absorbed in the thermallyconductive slug is ultimately transferred to the ambient atmosphere orto some external heat sink. The thermally conductive slug may be formedfrom a thermally conductive metal such as copper.

[0005] For example, U.S. Pat. No. 5,642,261 to Bond et al. discloses anintegrated circuit having a substrate in which an opening has beenformed to receive a thermally conductive slug. The integrated circuitdie is mounted on one side of the slug and the underside of the slug isexposed at the underside of the substrate. The integrated circuit die iswire bonded to the substrate and encapsulated in a conventional manner.Solder balls are attached to the underside of the substrate and of theslug in a ball grid array fashion for mounting on a circuit board. Whenthe integrated circuit package is mounted on a circuit board, a path ofhigh thermal conductivity is provided between the integrated circuit dieand the circuit board through the slug and the solder balls.

[0006] In another example, U.S. Pat. No. 5,693,572 to Bond et al.discloses a method for mounting an integrated circuit die within anintegrated circuit package in which the integrated circuit die ismounted on a thermally conductive slug. The slug is attached to anunderside portion of a substrate through which an opening has beenformed to receive the slug. The integrated circuit die is wire bonded tothe substrate and encapsulated in a conventional manner. Solder ballsare attached to the underside of the substrate in a ball grid arrayfashion for mounting on a circuit board. When the integrated circuitpackage is mounted on a circuit board, a path of high thermalconductivity is provided between the integrated circuit die and thecircuit board through the slug. The circuit board serves as a heat sink.

[0007] In an alternate embodiment of the invention disclosed in U.S.Pat. No. 5,693,572 to Bond et al. the integrated circuit die is placedwithin the opening that is formed in the substrate and the slug islocated below the plane of the underside of the substrate. The slug maybe epoxied or otherwise securely fastened to lateral surfaces of theunderside of the substrate. Such integrated circuit packages are alsothe subject of U.S. Pat. No. 5,991,156 to Bond et al. Experience hasshown that a very efficient method for attaching a thermally conductiveslug of the type described above is a solder reflow process.

[0008] Semiconductor devices that are packaged in a ball grid array(BGA) package are usually mounted onto a circuit board using a surfacemount process. During a surface mount process the temperature may exceedtwo hundred twenty degrees Celsius (220° C.). At this temperature thestrength of a solder connection is reduced to zero for a solder alloyhaving a melting temperature that is less than two hundred twentydegrees Celsius (220° C.). It is possible to use a solder alloy that hasa higher melting temperature but the use of such a solder alloy maycause irreversible damage to the substrate material.

[0009] Assume that a solder reflow process has been used to attach athermally conductive slug to an integrated circuit die in a ball gridarray package in the manner previously described in the prior art.During the surface mount process for mounting the ball grid arraypackage to a circuit board, the high temperature causes the solder sealof the thermally conductive slug to be weakened. The expansion ofmoisture diffused into a cavity of the integrated circuit package causesan increase in vapor pressure within the cavity. The increased vaporpressure then causes the thermally conductive slug to shift or move outof its original position. Alternatively, the increased vapor pressurecauses melted solder to ooze out from around the thermally conductiveslug. The soldered thermally conductive slug may generally be referredto as a soldered lid.

[0010] There is therefore a need in the art for an efficient system forventing pressure from an integrated circuit package that is sealed witha soldered lid. Specifically, there is a need in the art for a systemand method that is capable of providing a passage for moisture or vaporinside a cavity within a ball grid array integrated circuit package toescape from the cavity and reduce internal vapor pressure within thecavity.

[0011] Conductive epoxy can be used instead of solder to attach a lid toan integrated circuit die and substrate. However, if a continuous patchof epoxy material is applied the epoxy will stick to the integratedcircuit die, the substrate and the solder mask, and will seal the cavitywithin the integrated circuit package. When this happens, an increase invapor pressure caused by heating can cause an epoxied lid to move out ofits position in the same manner as that previously described for asoldered lid. The term “epoxied lid” refers to a lid that is glued toanother material using epoxy.

[0012] Therefore, there is also a need in the art for an efficientsystem and method for venting pressure from an integrated circuitpackage that is sealed with an epoxied lid.

SUMMARY OF THE INVENTION

[0013] To address the above-discussed deficiencies of the prior art, itis a primary object of the present invention to provide a system andmethod for venting pressure from an integrated circuit package that issealed with a lid using solder or epoxy as a sealing material.

[0014] In an advantageous embodiment of the invention for ventingpressure from an integrated circuit package that is sealed with asoldered lid, the invention comprises an integrated circuit comprising asubstrate having a top surface and a bottom surface, and having portionsthat form an opening through the substrate, and at least one metal layeron the substrate having portions that form a plurality of electricalconductors, and an integrated circuit die mounted within the openingthrough the substrate and electrically connected to the plurality ofelectrical conductors of the at least one metal layer, and a solder maskdeposited over portions of the at least one metal layer on the bottomsurface of the substrate. The solder mask is formed having a pluralityof solder mask vents that form a plurality of metal layer portions ofthe at least one metal layer around the opening on the bottom surface ofthe substrate.

[0015] The integrated circuit also comprises a lid having a top surfaceand a bottom surface. The lid is capable of covering the opening throughthe substrate when the lid is placed adjacent to the opening. The lid iscapable of being soldered to cover the opening by being soldered to theplurality of metal layer portions of the at least one metal layer aroundthe opening on the bottom surface of the substrate. The plurality ofsolder mask vents form a plurality of vapor pressure vents through thesolder material that is used to solder the lid to the plurality of metallayer portions. The vapor pressure vents prevent the occurrence of anyincrease in vapor pressure in the integrated circuit that would shiftthe soldered lid out of its soldered position.

[0016] An alternate advantageous embodiment of the invention is providedfor venting pressure from an integrated circuit package that is sealedwith an epoxied lid.

[0017] It is an object of the present invention to provide an integratedcircuit having a soldered lid in which the soldered lid does not moveout of its soldered position when heat is applied.

[0018] It is also an object of the present invention to provide anintegrated circuit with a soldered lid in which melted solder does notflow around the soldered lid when heat is applied.

[0019] It is yet another object of the present invention to provide anintegrated circuit having a solder mask that provides solder mask ventsthat form vapor pressure vents through solder material that is used tosolder a soldered lid to the integrated circuit.

[0020] It is another object of the present invention to provide a methodfor manufacturing an integrated circuit that is sealed with a solderedlid that is capable of venting pressure from the integrated circuit whenheat is applied to the integrated circuit during a surface mountprocess.

[0021] It is also an object of the present invention to provide anintegrated circuit having an epoxied lid in which the epoxied lid doesnot move out of its epoxied position when heat is applied.

[0022] It is also an object of the present invention to provide anintegrated circuit with an epoxied lid in which melted epoxy does notflow around the epoxied lid when heat is applied.

[0023] It is yet another object of the present invention to provide anintegrated circuit having vapor pressure vents through epoxy materialthat is used to epoxy an epoxied lid to the integrated circuit.

[0024] It is another object of the present invention to provide a methodfor manufacturing an integrated circuit that is sealed with an epoxiedlid that is capable of venting pressure from the integrated circuit whenheat is applied to the integrated circuit during a surface mountprocess.

[0025] The foregoing has outlined rather broadly the features andtechnical advantages of the present invention so that those skilled inthe art may better understand the detailed description of the inventionthat follows. Additional features and advantages of the invention willbe described hereinafter that form the subject of the claims of theinvention. Those skilled in the art should appreciate that they mayreadily use the conception and the specific embodiment disclosed as abasis for modifying or designing other structures for carrying out thesame purposes of the present invention. Those skilled in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the invention in its broadest form.

[0026] Before undertaking the Detailed Description of the Inventionbelow, it may be advantageous to set forth definitions of certain wordsand phrases used throughout this patent document: the terms “include”and “comprise,” as well as derivatives thereof, mean inclusion withoutlimitation; the term “or,” is inclusive, meaning and/or; the phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like; and theterm “controller” means any device, system or part thereof that controlsat least one operation, such a device may be implemented in hardware,firmware or software, or some combination of at least two of the same.In particular, a controller may comprise a data processor and anassociated memory that stores instructions that may be executed by thedata processor. It should be noted that the functionality associatedwith any particular controller might be centralized or distributed,whether locally or remotely. Definitions for certain words and phrasesare provided throughout this patent document, those of ordinary skill inthe art should understand that in many, if not most instances, suchdefinitions apply to prior uses, as well as future uses, of such definedwords and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] For a more complete understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings,wherein like numbers designate like objects, and in which:

[0028]FIG. 1 illustrates a bottom plan view of a prior art ball gridarray integrated circuit package in which a solder mask is indicated bya shaded portion and in which a placement of an integrated circuit dieis shown and in which a placement of a soldered lid is shown;

[0029]FIG. 2 illustrates a cross sectional view of the prior art ballgrid array integrated circuit package shown in FIG. 1 taken along lineA-A;

[0030]FIG. 3 illustrates a bottom plan view of a ball grid arrayintegrated circuit package in accordance with the principles of thepresent invention in which a solder mask having solder mask vents isindicated by a shaded portion and in which a placement of an integratedcircuit die is shown and in which a placement of a soldered lid isshown;

[0031]FIG. 4 illustrates a cross sectional view of the ball grid arrayintegrated circuit package shown in FIG. 3 taken along line B-B;

[0032]FIG. 5 illustrates a more detailed view of the central portion ofthe bottom plan view of the ball grid array integrated circuit packageshown in FIG. 3;

[0033]FIG. 6 illustrates a flow chart that shows an operation of anadvantageous embodiment of a first portion of a method of the presentinvention for manufacturing an integrated circuit having a soldered lid;

[0034]FIG. 7 illustrates a flow chart that shows an operation of anadvantageous embodiment of a second portion of a method of the presentinvention for manufacturing an integrated circuit having a soldered lid;

[0035]FIG. 8 illustrates a plan view of a prior art epoxy pattern placedon the surface of an integrated circuit die, substrate, and solder maskbefore the attachment of an epoxied lid;

[0036]FIG. 9 illustrates a plan view of an epoxy venting pattern of thepresent invention placed on the surface of an integrated circuit die,substrate, and solder mask before the attachment of an epoxied lid; and

[0037]FIG. 10 illustrates a flow chart that shows an operation of anadvantageous embodiment of a method of the present invention formanufacturing integrated circuit having an epoxied lid.

DETAILED DESCRIPTION OF THE INVENTION

[0038] FIGS. 1 to 10, discussed below, and the various embodiments usedto describe the principles of the present invention in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the invention. Those skilled in the artwill understand that the principles of the present invention may beimplemented in any suitably arranged integrated circuit package.

[0039]FIG. 1 illustrates a bottom plan view of an exemplary prior artball grid array (BGA) integrated circuit package 100. Integrated circuitpackage 100 comprises solder mask 110. The shaded portion of FIG. 1represents solder mask 110. Each of the plurality of circles shown inFIG. 1 represents a conventional solder ball 120. FIG. 2 illustrates across sectional view of the prior art ball grid array (BGA) integratedcircuit package 100 shown in FIG. 1 taken along line A-A.

[0040] By referring to FIG. 1 and to FIG. 2 it may be seen thatintegrated circuit package 100 comprises a substrate 210 having portionsthat form a square opening within the substrate 210 in the center of theintegrated circuit package 100. The present invention is not limited tothe use of a square opening. In other embodiments the opening may haveother geometrical forms (e.g., a rectangle). An integrated circuit die220 having a square shape is located within the square opening insubstrate 210. A lid 230 is placed over integrated circuit die 220 andis soldered into position over integrated circuit die 220 using a solderreflow process. Integrated circuit die 220 is wire bonded to metallayers 240 on substrate 210 and encapsulated in a conventional mannerwith mold compound 250.

[0041]FIG. 1 illustrates the location of the placement of integratedcircuit die 220 in the center of integrated circuit package 100.Integrated circuit die 220 is located within the dashed outline ofsquare 130. Proceeding outwardly from the dashed outline of square 130,the dashed outline of square 140 represents the boundary of the squareopening within substrate 210. FIG. 1 also illustrates the location ofthe placement of lid 230 over integrated circuit die 220. The solidoutline of square 150 represents the boundary of lid 230. The portion160 between the solid outline of square 150 and the interior edge ofsolder mask 110 represents the location of metal layer 240 on substrate210 near the edge of the opening in substrate 210.

[0042] As shown in FIG. 2, mold compound 250 extends through the openingin substrate 210 and covers the sides of integrated circuit die 220. Lid230 is soldered to metal layer 240 with solder 260. If the upper surfaceof lid 230 is not in contact with the lower surface of integratedcircuit die 220 then a cavity 270 is formed between lid 230 andintegrated circuit die 220.

[0043] As previously discussed, during the surface mount process formounting the ball grid array (BGA) integrated circuit package 100 to acircuit board the high temperature weakens solder 260 that fastens lid230 to metal layers 240. The expansion of moisture diffused into cavity270 causes an increase in vapor pressure within cavity 270. Theincreased vapor pressure may then cause lid 230 to shift or move out ofits original position. Alternatively, the increased vapor pressure maycause melted solder 260 to ooze out from around lid 230.

[0044] As will be more fully discussed, the present invention solvesthis problem by providing a ball grid array (BGA) integrated circuitpackage with solder mask vents for venting pressure that may build upwithin the integrated circuit package.

[0045]FIG. 3 illustrates a bottom plan view of an exemplary ball gridarray (BGA) integrated circuit package 300 in accordance with theprinciples of the present invention. Integrated circuit package 300comprises solder mask 310. The shaded portion of FIG. 3 representssolder mask 310. Each of the plurality of circles shown in FIG. 3represents a conventional solder ball 320. FIG. 4 illustrates a crosssectional view of the ball grid array (BGA) integrated circuit package300 shown in FIG. 3 taken along line B-B. As will be more fullydiscussed, solder mask 310 is formed having solder mask vents 315.

[0046] By referring to FIG. 3 and to FIG. 4 it may be seen thatintegrated circuit package 300 comprises a substrate 410 having portionsthat form a square opening within the substrate 410 in the center of theintegrated circuit package 300. The present invention is not limited tothe use of a square opening. In other embodiments the opening may haveother geometrical forms (e.g., a rectangle). An integrated circuit die420 having a square shape is located within the square opening insubstrate 410. A lid 430 is placed over integrated circuit die 420 andis soldered into position over integrated circuit die 420 using a solderreflow process. Integrated circuit die 420 is wire bonded to metallayers 440 on substrate 410 and encapsulated in a conventional mannerwith mold compound 450.

[0047]FIG. 5 illustrates a more detailed view of the central portion ofthe bottom plan view of the ball grid array (BFA) integrated circuitpackage 300 shown in FIG. 3. FIG. 5 illustrates the location of theplacement of integrated circuit die 420 in the center of integratedcircuit package 300. Integrated circuit die 420 is located within thedashed outline of square 330. Proceeding outwardly from the dashedoutline of square 330, the solid outline of square 340 represents theboundary of the square opening within substrate 410. As shown in FIGS.3, 4 and 5 solder mask 310 extends up to the boundary 340 of the squareopening within substrate 410.

[0048]FIG. 5 also illustrates the location of the placement of lid 430over integrated circuit die 420. The solid outline of square 350represents the boundary of lid 430. The portions (160 a, 160 b, 160 c,160 d, 160 e, 160 f, 160 g, 160 h) under the solid outline of square 350represent the location of metal layer 440 on substrate 410 near the edgeof the opening in substrate 410. Solder mask 310 is formed having aplurality of solder mask vents 315 that separate metal layer 440 intoseparate portions 160. In the embodiment shown in FIGS. 3, 4 and 5 thereare eight (8) portions (160 a -160 h) of metal layer 440. The numbereight is chosen as an example. In other embodiments metal layer 440 maybe separated into some other number of portions.

[0049] As shown in FIG. 4, mold compound 450 extends through the openingin substrate 410 and covers the sides of integrated circuit die 420. Lid430 is soldered to metal layer 440 with solder 460. If the upper surfaceof lid 430 is not in contact with the lower surface of integratedcircuit die 420 then a cavity 470 is formed between lid 430 andintegrated circuit die 420. Unlike lid 230 in prior art integratedcircuit package 100, lid 430 is not soldered to metal layer 440 in amanner that causes solder 460 to completely seal off cavity 470. Thesolder mask vents 315 of solder mask 310 provide a plurality of vaporpressure vents 480 through solder 460. The presence of a plurality ofvapor pressure vents 480 through solder 460 prevent vapor pressure frombuilding up in cavity 470 when integrated circuit package 300 issubjected to high temperature. The venting of vapor pressure insuresthat lid 430 is not moved out of its proper position during a surfacemount process.

[0050]FIG. 6 illustrates a flow chart that shows an operation of anadvantageous embodiment of a first portion of a method of the presentinvention for manufacturing an integrated circuit having a soldered lid.The steps of the first portion of the method shown in FIG. 6 arecollectively referred to with reference numeral 600.

[0051] In the first step a substrate 410 of integrated circuit 300 isprovided. Substrate 410 has a top surface and a bottom surface.Substrate 410 also has portions that form an opening through substrate410. (Step 610). Then at least one metal layer 440 is placed onsubstrate 410. Metal layer 440 has portions that form a plurality ofelectrical conductors. (Step 620). A solder mask 310 is then depositedover portions of metal layer 440 on the bottom surface of substrate 410.Solder mask 310 is formed having a plurality of solder mask vents thatform a plurality of metal layer portions 160 of metal layer 440 aroundthe opening on the bottom surface of substrate 410. (Step 630).

[0052] Solder material 260 is then applied over the metal areas of metallayer 440. (Step 640). A lid 430 is then provided that is large enoughto cover the opening through substrate 410 when lid 430 is placedadjacent to the opening through substrate 410. Lid 430 has a top surfaceand a bottom surface. Lid 430 is placed over the solder material 260 onmetal layer 440. (Step 650). The integrated circuit assembly is thenheated in a reflow oven. (Step 660). The heat from the reflow oven meltsthe solder material 260 to attach lid 430 to the plurality of metallayer portions 160 of metal layer 440 around the opening on the bottomsurface of substrate 410. (Step 670).

[0053]FIG. 7 illustrates a flow chart that shows an operation of anadvantageous embodiment of a second portion of a method of the presentinvention for manufacturing an integrated circuit having a soldered lid.The steps of the second portion of the method shown in FIG. 7 arecollectively referred to with reference numeral 700. Step 710 of FIG. 7follows step 670 of FIG. 6.

[0054] The solder mask vents form a plurality of vapor pressure vents480 through the solder 260 that is used to solder lid 430 to theplurality of metal layer portions 160. (Step 710). The vapor pressurevents 480 through the solder 260 prevent an increase in vapor pressurefrom occurring in cavity 270 between lid 430 and integrated circuit die420. (Step 720). There is therefore no increase in vapor pressure incavity 270 that would (1) shift lid 430 out of its desired solderedposition when solder 260 is heated, or (2) cause melted solder 260 toflow around lid 430 when solder 260 is heated.

[0055] Integrated circuit die 420 is then mounted within the openingthrough substrate 410. (Step 730). Integrated circuit die 420 is thenelectrically connected to the plurality of electrical conductors ofmetal layer 440. (Step 740). The integrated circuit assembly (comprisingsubstrate 410, integrated circuit die 420, and soldered lid 430) is thenplaced into a conventional mold (not shown). (Step 750). Mold compoundis then injected onto the top surface of substrate 410 to sealintegrated circuit 300 in a conventional integrated circuit package.(Step 760). Lastly, the mold compound is cured and a plurality of solderballs 320 is attached to the bottom surface of substrate 410. (Step770).

[0056] As previously mentioned, conductive epoxy can be used instead ofsolder to attach a lid to an integrated circuit die and substrate.However, if a continuous patch of epoxy material is applied, the epoxywill stick to the integrated circuit die, the substrate and the soldermask, and will seal the cavity within the integrated circuit package.When this happens, an increase in vapor pressure caused by heating cancause an epoxied lid to move out of its position in the same manner asthat previously described for an integrated circuit having a solderedlid.

[0057] An alternate advantageous embodiment of the invention is capableof venting pressure from an integrated circuit package that is sealedwith an epoxied lid. In this embodiment of the invention epoxy is placedon selected portions of the substrate and on selected portions of theintegrated circuit die. The placement of individual portions of epoxycreates one or more vapor pressure vents through the epoxy. The vaporpressure vents are capable of venting vapor pressure from an integratedcircuit having an epoxied lid in the same manner as that previouslydescribed for an integrated circuit having a soldered lid.

[0058]FIG. 8 illustrates a plan view of a prior art epoxy pattern placedon the surface of an integrated circuit die, substrate, and solder maskbefore the attachment of an epoxied lid. The central square in FIG. 8represents the location of an integrated circuit die 810. The darklyshaded peripheral portion shown in FIG. 8 represents the location ofsolder mask 820. The lightly shaded portion of FIG. 8 that fully coversintegrated circuit die 810 and that extends to the location of soldermask 820 represents a prior art epoxy pattern 830.

[0059] Applying epoxy in accordance with prior art epoxy pattern 830will cause the epoxy to fully cover the opening in the substrate inwhich integrated circuit die 810 is located. An epoxy lid (not shown inFIG. 8) is then set in position on the epoxy pattern and the epoxy iscured. The epoxy lid will then completely seal the bottom of integratedcircuit die 810. As previously described, heating may cause an increasein vapor pressure within a cavity in the integrated circuit. This maycause the epoxy lid to move out of its position or the epoxy material toflow around the epoxy lid.

[0060]FIG. 9 illustrates a plan view of an epoxy venting pattern of thepresent invention placed on the surface of an integrated circuit die,substrate, and solder mask before the attachment of an epoxied lid. Thelightly shaded central square in FIG. 9 represents the location of anintegrated circuit die 910. The darkly shaded peripheral portion shownin FIG. 9 represents the location of solder mask 920. The eight (8)lightly shaded portions of FIG. 9 that extend from solder mask 920 tointegrated circuit die 910 represent a partial epoxy pattern 930. Theeight (8) white portions between each of the eight (8) lightly shadedportions of partial epoxy pattern 930 represent a plurality of vaporpressure vents 940. Mold compound may extend into the plurality of vaporpressure vents 940.

[0061] Applying epoxy in accordance with epoxy pattern 930 will causethe epoxy to provide vapor pressure vents 940 so that the opening in thesubstrate in which integrated circuit die 910 is located will not becompletely sealed off. An epoxy lid (not shown in FIG. 9) is then set inposition on the epoxy pattern and the epoxy is cured. Vapor pressurevents 940 will prevent the epoxy lid from completely sealing off thebottom region of integrated circuit die 910 and mold compound. The epoxypattern 930 of the present invention provides vapor pressure vents 940to vent any increase in vapor pressure within a cavity of the integratedcircuit.

[0062]FIG. 10 illustrates a flow chart that shows an operation of anadvantageous embodiment of a method of the present invention formanufacturing an integrated circuit having an epoxied lid. The steps ofthe method shown in FIG. 10 are collectively referred to with referencenumeral 1000.

[0063] The flow chart shown in FIG. 10 describes the method in generalterms. In the first step a substrate for an integrated circuit isprovided. The substrate has a top surface and a bottom surface. Thesubstrate also has portions that form an opening through the substrate.Then at least one metal layer having electrical conductors is placed onthe substrate. (Step 1010). A tape is then placed across the bottomsurface of the opening in the substrate. The tape is capable of holdingan integrated circuit die. (Step 1020).

[0064] An integrated circuit die (IC die) is then placed within theopening through the substrate and held in place by the tape. (Step1030). Then the integrated circuit die is wire bonded to the metallayer. Mold compound is then applied to seal and protect the integratedcircuit die within the integrated circuit. The mold compound is curedand hardened. Because the mold compound now holds the integrated circuitdie is place within the opening in the substrate, the tape is nowremoved from the bottom of the substrate. (Step 1040).

[0065] Epoxy material is then applied to the bottom of the integratedcircuit die. The epoxy material is applied in accordance with the epoxypattern of the present invention in order to form vapor pressure ventsthrough the epoxy material. (Step 1050). An epoxy lid is then providedthat is large enough to cover the opening through the substrate when theepoxy lid is placed adjacent to the opening through the substrate. Theepoxy lid has a top surface and a bottom surface. When epoxy lid is inplace, then the epoxy is heated in a reflow oven. The heat from thereflow oven melts and cures the epoxy to attach the epoxy lid to thebottom of the integrated circuit die. (Step 1060). Lastly, a pluralityof solder balls is attached to the bottom surface of the substrate.(Step 1070).

[0066] Although the present invention has been described in detail,those skilled in the art should understand that they could make variouschanges, substitutions and alterations herein without departing from thespirit and scope of the invention in its broadest form.

1. An integrated circuit comprising: a substrate having an openingtherethrough; at least one metal layer on said substrate having portionsthat form a plurality of electrical conductors; an integrated circuitdie mounted within said opening through said substrate and electricallyconnected to said plurality of electrical conductors of said at leastone metal layer; and a solder mask deposited over portions of said atleast one metal layer, wherein said solder mask is formed having aplurality of solder mask vents around said opening.
 2. An integratedcircuit as claimed in claim 1 further comprising: a lid covering saidopening through said substrate when soldered to portions of said atleast one metal layer around said opening; wherein said plurality ofsolder mask vents result in a plurality of vapor pressure vents througha solder material when said solder material is used to solder said lidto said portions of said at least one metal layer.
 3. The integratedcircuit as claimed in claim 2 wherein said vapor pressure vents throughsaid solder material prevent an increase in vapor pressure fromoccurring in a cavity within said integrated circuit.
 4. The integratedcircuit as claimed in claim 2 wherein said vapor pressure vents throughsaid solder material prevent occurrence of one of: a shift of said lidout of a desired soldered position when said solder material is heated;and a flow of melted solder around said lid when said solder material isheated.
 5. The integrated circuit as claimed in claim 2 wherein said lidcomprises a thermally conductive material.
 6. The integrated circuit asclaimed in claim 2 wherein said lid comprises a metal.
 7. The integratedcircuit as claimed in claim 2 further comprising a plurality of solderballs in electrical connection with said plurality of electricalconductors.
 8. The integrated circuit as claimed in claim 2 furthercomprising a mold compound encapsulating said substrate and saidintegrated circuit die within said opening.
 9. The integrated circuit asclaimed in claim 1 wherein a shape of said opening though said substrateis square and a shape of said integrated circuit die is square.
 10. Theintegrated circuit as claimed in claim 9 wherein said plurality ofsolder mask vents comprise at least one solder mask vent on each side ofsaid square integrated circuit die.
 11. A method of fabricating anintegrated circuit, said method comprising providing a substrate havingan opening therethrough, and at least one metal layer thereon forming aplurality of electrical conductors; mounting an integrated circuit diewithin said opening through said substrate and electrically connectingsaid integrated circuit die to said plurality of electrical conductorsof said at least one metal layer; and depositing a solder mask overportions of said at least one metal layer, wherein said solder mask isformed having a plurality of solder mask vents around said opening. 12.The method as claimed in claim 11 further comprising: soldering a lidover said opening and to portions of said at least one metal layeraround said opening, wherein said plurality of solder mask vents form aplurality of vapor pressure vents through a solder material when saidsolder material is used to solder said lid to said portions of said atleast one metal layer.
 13. The method as claimed in claim 12 furthercomprising: venting vapor pressure through said vapor pressure ventsthrough said solder material to prevent an increase in vapor pressurefrom occurring in a cavity within said integrated circuit.
 14. Themethod as claimed in claim 12 further comprising: venting vapor pressurethrough said vapor pressure vents through said solder material toprevent occurrence of one of: a shift of said lid out of a desiredsoldered position when said solder material is heated, and a flow ofmelted solder around said lid when said solder material is heated. 15.The method as claimed in claim 12 wherein said lid comprises a thermallyconductive material.
 16. The method as claimed in claim 12 wherein saidlid comprises a metal.
 17. The method as claimed in claim 12 furthercomprising: electrically connecting a plurality of solder balls withsaid plurality of electrical conductors; and making a connection withsaid plurality of solder balls to a circuit board.
 18. The method asclaimed in claim 12 further comprising: encapsulating with a moldcompound, a surface of said substrate and said integrated circuit diewithin said opening of said substrate.
 19. The method as claimed inclaim 11 wherein a shape of said opening though said substrate is squareand a shape of said integrated circuit die is square.
 20. The method asclaimed in claim 19 wherein said plurality of solder mask vents compriseat least one solder mask vent on each side of said square integratedcircuit die.
 21. An integrated circuit comprising: a substrate having anopening therethrough; at least one metal layer on said substrate havingportions that form a plurality of electrical conductors; an integratedcircuit die mounted within said opening through said substrate andelectrically connected to said plurality of electrical conductors ofsaid at least one metal layer; and epoxy deposited over portions of saidsubstrate and said integrated circuit and having a plurality of vaporpressure vents.
 22. An integrated circuit as claimed in claim 21 furthercomprising: a lid attached by said epoxy over said opening, wherein saidplurality of vapor pressure vents within said epoxy prevent an increasein vapor pressure from occurring in a cavity within said integratedcircuit.
 23. The integrated circuit as claimed in claim 22 wherein saidplurality of vapor pressure vents through said epoxy prevent theoccurrence of one of: a shift of said lid out of a desired epoxiedposition when said integrated circuit is heated; and a flow of meltedepoxy around said lid when said integrated circuit is heated.
 24. Theintegrated circuit as claimed in claim 22 wherein said lid comprises athermally conductive material.
 25. A method of fabricating an integratedcircuit, said method comprising: providing a substrate having an openingtherethrough; and at least one metal layer thereon having portions thatform a plurality of electrical conductors; mounting an integratedcircuit die within said opening through said substrate and electricallyconnecting said integrated circuit die to said plurality of electricalconductors of said at least one metal layer; and depositing epoxy overportions of said substrate and said integrated circuit die, wherein saidepoxy layer is formed having a plurality of vapor pressure vents. 26.The method as claimed in claim 25 further comprising: attaching a lidover said opening with epoxy; and venting vapor pressure through saidvapor pressure vents in said epoxy layer to prevent an increase in vaporpressure from occurring in a cavity within said integrated circuit. 27.The method as claimed in claim 26 further comprising: venting vaporpressure through said vapor pressure vents in said epoxy layer toprevent the occurrence of one of: a shift of said lid out of a desiredepoxied position when said integrated circuit is heated, and a flow ofmelted epoxy around said lid when said integrated circuit is heated. 28.The method as claimed in claim 26 wherein said lid comprises a thermallyconductive material.